.Header{
    position: fixed;
    top:0;
    left:0;
    width:100%;
    height: 45px;
    line-height: 45px;
    text-align: center;
    font-size: 16px;
    color:red;
    background-color: #fff;
}
.Header p{
    margin: 0;
}
.Header span{
    float: left;
}
body{
    padding-top: 50px;
}